Tool made from plastic

ABSTRACT

The invention relates to a tool comprising a partial region made from plastic, in which a material with slide bearing properties is inlaid. Said tool is a moulding tool, which can be applied, for example, in the deep-drawing of metal pieces. The partial region in which the material with slide bearing properties, for example graphite, is inlaid, is a front layer ( 11 ) of the tool, comprising the moulding region thereof. The backing ( 12 ) of the tool is also made from plastic, which can optionally contain conventional fillers. The front layer ( 11 ) of the tool, reinforced, for example, with graphite, permits a deep drawing optionally without the use of lubricants, whereby the moulding region of the tool has good slide bearing properties and a high pressure resistance.

The present invention relates to a tool including a section made of a plastic, in which a material with lubricating properties is embedded.

Tools made of steel or gray cast iron are conventionally used for forming processes, deep-drawing processes. More recently, forming tools made at least partially of plastic have also become known, which can be used for certain applications, such as for small series. For example, DE 199 00 597 A1 describes a sheet metal forming tool and a method for its production, in which the tool is manufactured with layers of plastic films that are glued on top of each other one after another. In this process, plastic powder can also be filled, layer by layer, into a working space and then sintered by means of a laser beam. However, the processes described in this document are relatively complex and, furthermore, such tools are only feasible for the forming of workpieces that are produced in small series with limited numbers of production units.

DE 93 18 272.4 U1 describes a tool for the non-cutting forming of workpieces, with the tool per se being made of a metallic material, especially gray cast iron, while a guide component of the tool, which has a slide face, is made of a duroplastic with a fiber or woven material insert and embedded laminar graphite. This is done to improve the lubricating properties and reduce wear. This known tool is made only partially of plastic in the region of tool components that are displaceable relative to one another, such as slides and the like, but not in the forming regions themselves, in which the tool acts on a workpiece. Instead, a bending die that forms a forming region of the tool is made of metal.

The object of the present invention is to provide a tool made of an alternative material and having advantageous properties in comparison to conventional tools.

This object is attained by providing a tool according to the invention of the type stated initially, having the characterizing features of the principal claim. According to the invention, the tool is a forming tool and the section made of plastic, in which a material with lubricating properties is embedded in the plastic, is a forming region of the tool. The abovementioned section of the tool, made of a plastic in which a material with lubricating properties is embedded, preferably includes a front layer of the tool. This section of the tool can contain graphite, for example, as a material with lubricating properties. The plastic of the tool preferably contains graphite powder in this section, especially graphite powder with a particle size of between approximately 50 and approximately 250 μm. The thickness of the abovementioned front layer in the forming region of the tool, in which the plastic contains a material with lubricating properties, is preferably at least approximately 5 mm. For example, the thickness of this front layer lies within a range of between approximately 5 and approximately 15 mm.

A preferred embodiment of the object attained according to the invention provides that not only the forming region of the tool is made of plastic, but that the tool also has a rear structure essentially made of plastic. Accordingly, the entire tool can be made of plastic, although only the section that forms the forming region must be made of a plastic in which a material with lubricating properties is embedded. A less expensive material can be used for the rear structure. The rear structure of the tool is preferably made of a plastic containing a filler. Fillers such as, for example, aluminum and/or gray cast iron and/or sand, preferably in powdered form, are possible. Thus, the rear structure is made of a material having sufficient resistance to pressure. The rear structure can, for example, be made of a full cast material including the plastic and the filler or fillers. On the one hand, the front layer of the tool, which serves as the forming region, has increased resistance to pressure in the regions that come into contact with the workpiece to be formed, while the lubricating capacity in the region of the contact surface is assured by the embedded material with lubricating properties. A self-lubricating effect is essentially achieved in the forming region, i.e., in the region of the front surface of the tool, thus enabling the use of conventional lubricants to be entirely or largely eliminated.

Within the scope of the present invention, the production of deep-drawing tools is preferred. These tools can be, for example, dies, hold-down devices, or female dies, especially for the deep-drawing of metal parts. The deep-drawing tools according to the invention are especially suitable for the forming of metal parts, e.g., in automobile or aircraft production. Embedding the material with lubricating properties prevents, during the deep-drawing of a metal plate, for example, which is stressed in this process in a tensile direction perpendicular to the direction of motion of the deep-drawing tool, particles, especially filler particles, from being torn out of the plastic matrix, resulting in cracks in the tool.

The advantages of the plastic tools made with the materials according to the invention, in comparison to conventional steel tools, lie, for example, in the material costs, which are reduced by up to about 70%. The plastics used to manufacture the tools are more easily machined, reducing the use of machinery in production of the tools. Energy and output requirements during the machining work required to produce the tools can be reduced by 65%, for example. The break-in time is also shorter than with steel tools, by up to 60%, for example. The use of plastics according to the invention for production of the tools leads to a substantial reduction in weight of up to 60%, for example, and thus to a reduction in loads on crane equipment. The tools can be modified more flexibly and cost-effectively, thereby achieving a high degree of cost, time, and energy savings. The tools are also suitable for recycling, because they can be fully recycled as filler material in the production of new plastic tools, thus eliminating disposal costs.

The elastic behavior of the plastics results in improvement of the quality of the formed workpieces. Embedding graphite in the plastic of the tools produces a self-lubricating effect on the contact surfaces of the tool. If it is even necessary to additionally use liquid lubricants during forming, the amount of lubricant necessary can be significantly reduced, for example, by approximately 3 g/m². The frictional conditions during deep-drawing are improved by incorporating graphite powder into the plastic. As a result of the elimination of or reduction in liquid lubricants during deep-drawing, dirt accumulation in the work area is significantly reduced, thereby benefiting the environment.

The preferred modular construction of the plastic tools according to the invention, including the front layer (forming region) and the rear structure, allows for the reuse of a large portion of the tools. Because of the incorporation of the material with lubricating properties into the front layer and the resulting elimination (for the most part) of liquid lubricants, the need to degrease the finished drawn parts is also eliminated, as a rule. The features specified in the subclaims relate to preferred embodiments of the solution of the object attained according to the invention. Further advantages of the invention can be inferred from the following detailed description.

In the following, the invention will be explained in greater detail, using exemplary embodiments with reference to the attached drawings, which show

FIG. 1 a highly schematically simplified perspective view to explain a deep-drawing process by means of a tool according to the invention;

FIG. 2 a second schematically simplified view to explain the deep-drawing process;

FIG. 3 a schematically simplified perspective view of a tool according to the invention installed into a deep-drawing device;

FIG. 4 a perspective view of a finished part, which was deep-drawn by means of a tool according to the invention.

First, we refer to FIG. 1. The drawing shows, in a highly schematically simplified perspective view, an array of tools for deep-drawing a sheet metal component 10. An upper tool part 8 is provided for forming the sheet metal component 10 in a deep-drawing process, as well as a lower tool part 9 in the form of a female die that accepts the upper tool part 8. The upper tool part 8 includes a rear structure 12 of plastic and a front layer 11 that forms the forming region, which is also made of plastic; however, a graphite powder 7 is embedded in this plastic to achieve a self-lubricating effect while forming a sheet metal component 10.

As a rule, the plastic that forms the rear structure 12 of the tool also contains fillers, although they can be fillers of a conventional nature, so as to provide the tool with certain desired characteristics, such as ensuring that the rear structure 12 has an adequate resistance to pressure. The lower tool part 9 is also made of plastic; a conventional plastic can be used here as well, provided it is not used in the forming regions. It is recommended, however, even in the lower tool part 9, that the regions that come into contact with the sheet metal 10 to be deep-drawn during the forming process be made of a plastic with the incorporated lubricating material. This is specified in greater detail below, with reference to FIG. 2, which illustrates, in a schematically simplified depiction, the forces acting during the deep-drawing process.

FIG. 2 shows the position of a sheet metal component 10 between the front layers 11 of an upper tool part 8 and a lower tool part 9. In both cases, the front layers 11, which are made of plastic, contain an embedded graphite powder 7 to achieve the lubricating effect. In the drawing, the arrow indicates that, during the deep-drawing process, a shearing force acts on the sheet metal 10 as well as on the front surfaces of the two tools, which essentially acts perpendicularly to the direction of motion of the tools. As a result of this shearing stress between the sheet metal 10 and the front layers 11 of the upper tool part 8 and lower tool part 9, each provided with embedded graphite, a lubricating effect is achieved which is attributable to the lubricating properties of the graphite. This eliminates the need to use a liquid lubricant. Moreover, it was found that, as a result of embedding the graphite in the respective front layers 11 of the tools, their resistance to pressure at the contact surface is also increased.

Using a drawing die of the type depicted schematically in FIG. 2, several hundred parts were drawn. Then the condition of the tool was examined, and it was concluded that it would easily allow for the drawing of thousands of additional parts.

FIG. 3 shows, once again and somewhat more precisely, a section of deep-drawing device in perspective view in which it is possible to discern the plastic rear structure 12 of the tool, which is fastened to an upper plate 20 of the device, which is lowered during the deep-drawing process. This lowering of the plate 20 and the tool made of plastic takes place in a tool guide 14 of the device, which will not be explained in greater detail here.

The front layer 11 of the tool, provided with embedded graphite and also made of plastic, as well as the hold-down devices 13 of the device, located beneath this front layer, are also visible in FIG. 3.

FIG. 4 shows a perspective view of a metal component that was deep-drawn from a piece of sheet metal by means of a tool of the type according to the invention. It is a shielding plate 15 for a motor vehicle. As can be seen, the shielding plate 15 has, following the forming process, convex curved regions 18 as well as concave curved regions 19. The shielding plate 15 also has various perforations 16 as well as formed areas incorporated during the deep-drawing process, such as the well-like depression 17 recognizable in the drawing. It was found that such metal components can be deep-drawn in outstanding quality with the tools according to the invention.

List of Reference Characters

7 Graphite Powder

8 Upper Tool Part

9 Lower Tool Part

10 Sheet Metal Component

11 Front Layer

12 Rear Structure

13 Hold-down Device

14 Tool Guide

15 Shielding Plate

16 Perforations

17 Depression

18 Convex Curved Area

19 Concave Curved Area

20 Plate 

1. A tool comprising a section made of a plastic, wherein a material with lubricating properties is embedded in the plastic, the tool is a forming tool, and the section made of plastic is a forming region of the tool.
 2. The tool according to claim 1, wherein the section made of plastic comprises a front layer of the tool.
 3. The tool according to claim 1, wherein the material with lubricating properties is graphite.
 4. The tool according to claim 3, wherein the graphite is graphite powder.
 5. The tool according to claim 4, wherein the graphite powder has a particle size between approximately 50 and approximately 250 μm.
 6. The tool according to claim 2, wherein the thickness of the front layer is at least 5 mm.
 7. The tool according to claim 6, wherein the thickness of the front layer is between approximately 5 and approximately 15 mm.
 8. The tool according to claim 1 further comprising a rear structure made primarily of plastic.
 9. The tool according to claim 8, wherein the plastic of the rear structure contains a filler.
 10. The tool according to claim 9, wherein the filler is selected from the group consisting of aluminum, gray cast iron, sand, and mixtures thereof. 11-13. (Canceled)
 14. The tool according to claim 10, wherein the filler is in powder form.
 15. The tool according to claim 1, wherein the forming tool is a deep-drawing tool.
 16. The tool according to claim 1, wherein the forming tool is a die, hold-down device, or female die for the deep-drawing of metal parts.
 17. The tool according to claim 1, wherein the forming tool is a deep-drawing tool for forming metal parts for automobile construction or aircraft construction.
 18. A process for the formation of a part comprising the steps of obtaining a workpiece and subject the workpiece to the action of a tool according to claim
 1. 19. The process of claim 18, wherein the process is a deep-drawing process, and the workpiece is sheet metal. 